In conventional dilation techniques used in intraocular surgery, the pupil is dilated by a mydriatic agent. However, when mydriatic agents are employed the surgeon does not know, with certainty, either the diameter or duration of the dilation. When the pupil is--or becomes--insufficiently dilated the performance of the surgeon is hindered. Not only may the patient results then be adversely affected, but the instruments used by the surgeon may injure intraocular structures, for example causing iritis.
Conventional dilation techniques have the further drawback of requiring the use of miotic agents to constrict the pupil after the surgical procedure is completed.
In some instances, the above-indicated techniques may require alternative performance of an iridectomy.
Because of the problems caused by the conventional mydriatic-agent-followed-by-miotic-agent steps, attempts have been made to provide dilation means that are mechanical instead of pharmacological. The mechanical dilation means known to applicant are, however, characterized by various shortcomings. The shortcomings include one or more of the following: 1) inability to effect precise control of the amount of dilation, 2) relative difficulty or complexity of insertion, removal, and use, and 3) failure to shield the surrounding edge of the iris, etc., from surgical instruments.